Crank-connecting rod mechanism

ABSTRACT

A crank-connecting rod mechanism for an internal combustion engine or the like comprising a shaft rotating around its axis, a first crank fixed to the shaft and a crank pin fixed to the first crank. A crank pin extends parallel to but at a first radial distance from the shaft. A second crank rotatably mounted onto the first crank pin is fixed to a second crank pin having an axis at a second radial distance from the axis of the first crank pin. A connecting rod is rotatably mounted on the second crank pin. Rotary means are provided to force the second crank to rotate relative to the first crank upon a rotation of the shaft.

This application is a national stage filing under 35 U.S.C. § 371 and ishereby claimed of International application PCT/NL99/00309, filed May19, 1999 and published in English.

BACKGROUND OF THE INVENTION

The invention relates to a crank-connecting rod mechanism for aninternal combustion engine or the like.

The present crankshaft as used in all standard piston engines is alreadyseveral decades old and its principle has remained unchanged. Althoughconstant refinements have resulted in a highly reliable and trouble-freecrank mechanism, the mechanism clearly has its limitations.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a crank-connecting rodmechanism which offers surprising new possibilities.

In order to accomplish that objective, the present invention provides acrank-connecting rod mechanism for an internal combustion engine or thelike, which comprises a shaft rotating about its axis, a first crankfixed to said shaft, a crank pin fixed to said first crank, whichextends parallel to but at a first radial distance from said shaft, asecond crank rotatably mounted on the first crank pin, which is fixed toa second crank pin having an axis at a second radial distance from theaxis of the first crank pin, a connecting rod which is rotatably mountedon the second crank pin, as well as rotary means to force the secondcrank to rotate relative to the first crank upon rotation of the shaft.

In certain uses, significant benefits can be obtained from the additionof an additional crank comprising rotary means which determine therotation of the second crank relative to the first crank.

In the case of two-stroke engines, for example, it is advantageous ifthe rotary means are so arranged that the second crank rotates at thesame speed, while in an opposite direction, as the first crank, in whichcase the first radial distance is preferably the same as the secondradial distance.

The use of such a crank-connecting rod mechanism makes it possible tohave the connecting rod move straight up and down, in that the two crankpins rotating in opposite directions neutralize each other's movementsin a direction perpendicularly to the connecting rod whilst enhancingsaid movements in the direction of the connecting rod. The connectingrod thus has linear bearings. This offers several advantages. In thefirst place, hardly any transverse forces will occur between the pistonand the cylinder wall (the so-called guideway forces), due to the factthat the connecting rod moves straight up and down. The risk of seizingpistons and the friction between piston wall and cylinder wall are thusreduced. Further, a close fit rather than the use of a piston springcould provide a seal between the piston and the cylinder, which reducesthe need for lubrication. The mechanism can furthermore be completelybalanced for each individual cylinder, so that a low-vibration operationis possible with a one-cylinder engine as well. The construction makesit possible to use a simple suction membrane, wherein the so-called“false volume” (between membrane and the underside of the piston) can beminimized, as a result of which suction and filling are enhanced.Further, a connecting rod which does not move outwards in a lateraldirection enables a longer stroke of the piston, wherein the port designcan be optimized. The suction volume can be influenced by means of asuitable selection of the diameter of the connecting rod, by which thecompression/expansion ratio can be determined. Finally, the constructionis very advantageous for an opposed cylinder arrangement, wherein apiston can be mounted on either side of the same connecting rod.

Another possibility which the crank-connecting rod mechanism accordingto the present invention offers is the adjustability of the compressionratio, which may be important in particular with four-stroke engines.Such adjustability can be achieved by rotating the second crank withrespect to the first crank in the top dead center, which makes itpossible to change the straight up-and-down movement. of the secondcrank pin into a more or less oblique movement of the second crank pin.This results in a position change of the bottom and the top dead center.The top dead center will be utilized in the lower part load ranges ofthe running internal combustion engine, as a result of which the finalcompression pressure can reach the correct level in spite of the lowsuction pressure. In the middle part load range up to atmosphericsuction, the top dead center will have to be reduced so far that anormal compression ratio is reached.

Adjustment of the crank pins relative to each other can be easilyeffected when said rotary means comprises of at least two parts, a firstpart of which is rotatably mounted on the second shaft and fixedlyconnected to the second crank, and a second part which is in engagementwith the first part and which is adjustable with respect to thecrankcase. In a practical embodiment thereof, said first part is a gearand said second part is a internal ring gear, with which the first gearmeshes. In that case, the ring gear can be adjusted through an angleupon transition to another load range during operation of thecrank-connecting rod mechanism so as to adjust the movement of thesecond crank pin and thus of the bottom and the top dead center.

Another interesting use of the crank-connecting rod mechanism ispossible with a four-stroke engine, where it can be used to achieve adifferent length ratio between the expansion stroke and the compressionstroke. This can for example be achieved in that the rotary means are soarranged that the second crank rotates at half the speed, albeit anopposite direction, of the first crank, whereby preferably the firstcrank is positioned at 0° and the second crank is positioned atsubstantially 90° at the uppermost point of the compression stroke, sothat the first and the second stroke are both positioned atsubstantially 180° at the end of the expansion stroke. A complete rotarycycle will comprise two revolutions of the first crank in that case, andthe ratio between the expansion stroke and the compression stroke can bedetermined by selecting the first and the second radial distance.

This embodiment has a number of significant advantages:

In the first place it is possible to achieve a long expansion stroke inthis manner, so as to maximize utilization of the expansion energy andminimize the pressure upon opening of the exhaust valve. The relativelylarge expansion ratio will result in an increase of the theoreticefficiency.

Also in this embodiment, the connecting rod makes a much straightermovement during the expansion stroke than usual, as a result of whichthe guideway forces are significantly reduced. This leads to reducedfriction losses and thus to enhanced mechanical efficiency.

Due to the possibilities of using the high-pressure turbine/compressor(up to 3.5 bars) in combination with the adjustable top dead center ofthe piston, the same engine power can be achieved with a pistondisplacement of about 30% of that of a conventional engine which doesnot employ supercharging. As a result, the pumping losses during partload operation of the engine will be much smaller, so that themechanical efficiency during part load operation is considerablyenhanced. In one embodiment, wherein the piston stroke is adjustable, alow compression ratio can be selected when a high boost pressure isused, and a favorable gas exchange can take place, while the compressionratio can be increased and an increased gas residue can be recycled whena low boost pressure is used.

The piston travels at a lower speed at the end of the compressionstroke, so that less pre-ignition is required.

Also during part load less pre-ignition is required, because) the finalcompression pressure remains high, due to the adjustable top dead centerposition of the piston.

When using a high-pressure turbine/compressor, it is possible to use arelatively small engine, as a result of which the weight of the enginecan remain at the same level as that of the current engines in spite ofthe increased number of engine parts.

Based on the aforesaid advantages, an efficiency enhancement during partload of approx. 50-70% may be possible, while an overall efficiencyenhancement of 30-50% can be realised with an average driving style.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail hereafter with referenceto the drawings, which show embodiments of the crank-connecting rodmechanism according to the invention.

FIG. 1 is a perspective exploded view of a number of parts of a firstembodiment of the crank-connecting rod mechanism according to theinvention in longitudinal sectional view thereof.

FIG. 2 is a longitudinal sectional view of the parts of FIG. 1.

FIG. 3 is a perspective exploded view of a crank-connecting rodmechanism according to the principle of FIGS. 1 and 2.

FIGS. 4a-i are side views of the crank-connecting rod mechanism of FIG.3, showing nine positions thereof during one revolution of thecrankshaft.

FIG. 5 is an exploded view of a variant of the first embodiment of acrank-connecting rod mechanism according to the invention.

FIG. 6 is a partially cut-away, perspective view of the crank-connectingrod mechanism of FIG. 5.

FIG. 7 is a cut-away, perspective view of a two-stroke piston enginecomprising the crank-connecting rod mechanism of FIG. 6.

FIGS. 8a-i are views comparable to FIGS. 4a-i of another embodiment ofthe crank-connecting rod mechanism according to the invention for afour-stroke engine, showing nine positions thereof during tworevolutions of the crankshaft.

FIGS. 9a-d show the crank-connecting rod mechanism of FIG. 5 in fourdifferent positions thereof, with the ring gear thereof slightlyrotated.

FIG. 10 is an exploded view of a practical embodiment of thecrank-connecting rod mechanism of FIGS. 8 and 9.

FIG. 11 is an enlarged, partially cut-away, perspective view of theconnecting rod with the second crank of the crank-connecting rodmechanism of FIG. 10.

FIG. 12 is a perspective view of a variant of the crank-connecting rodmechanism of FIG. 10 for use in a multi-cylinder engine comprisingcylinders arranged in the form of a V or in flat opposite relationship.

FIG. 13 is a schematic, vertical sectional view of another variant ofthe crank-connecting rod mechanism according to the invention as used ina four-cylinder four-stroke in-line engine.

FIG. 14 is a perspective view of the dismounted crank-connecting rodmechanism of FIG. 13.

FIG. 15 is an exploded view of the crankshaft of the crank-connectingrod mechanism of FIGS. 13 and 14.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

FIGS. 1 and 2 show the principle of the crank-connecting rod mechanismaccording to the invention in very schematic form. The mechanismcomprises a shaft 1, which is rotatably mounted in bearings (not shown),whereby it is capable of rotation about its axis. A first crank 2 isformed on said shaft 1, in this embodiment in the form of a concentricdisc, which eccentrically supports a first crank pin 3 which extendsparallel to shaft 1, but which projects from the other side of firstcrank 2. The axis of first crank pin 3 is located at a radial distanceR₁ from the axis of shaft 1.

A second crank 4 is rotatably mounted on first crank pin 3 by means of abearing (not shown), wherein the hole 5 in the second crank 4 that fitsround first crank pin 3 is positioned eccentrically with respect tosecond crank 4. A second crank pin 6 is formed on second crank 4, whichcrank pin 6 is not exposed to view in this figure because it coincideswith the second crank. As it is, a bearing 11 of a connecting rod 12(see FIG. 3) surrounds second crank 4, and consequently the axis ofsecond crank 4 will function as the axis of the second crank pin 6. Theaxis of second crank pin 6 is disposed at a distance R₂ from the axis offirst crank pin 3.

According to the invention, second crank 4 must rotate about first crankpin 3 in a controlled manner, and to this end rotary means 7 areprovided, which are provided in this embodiment with a gear 8 which isfixed to second crank 4 and with a ring gear 9 which may or may not berotatably connected to the crankcase of the crank-connecting rodmechanism. In the illustrated embodiment, gear 8 is bearing-mounted onfirst crank pin 3 between first crank 2 and second crank 4 so as toobtain a compact construction. Gear 8 is fitted with a counterweight 10which functions to balance the mechanism.

The engagement between gear 8 and ring gear 9 and the presence of gear 8on first crank pin 3 ensure that gear 8 will roll over ring gear 9 uponrotation of shaft 1 and the resulting circular movement of first crankpin 3, therefore, whereby it is rotated in a direction opposed to thedirection of rotation of shaft 1, so that the second crank 4 connectedto gear 8 on the one hand follows the movement of the first crank pin 3,but in addition makes a rotation in opposite direction. Variousmovements of the second crank pin 6 or of the bearing-mounted connectingrod 12 thereon can be effected by suitably selecting the radialdistances R₁ and R₂ and a radius R₃ of gear 8, and furthermore theinitial angular position of the second crank pin 6 with respect to thefirst crank pin 3.

In the illustrated embodiment, it applies that R₁=R₂=R₃. This impliesthat second crank 4 on first crank pin. 3 rotates at the same speed asshaft 1, albeit in opposite direction, while in the illustrated positionevery horizontal movement of the first crank pin 3 is compensated by thehorizontal movement in opposite direction of the second crank pin 6, sothat the second crank pin 6 indeed makes a rotary movement but movesvertically up and down thereby.

FIGS. 3 and 4a-i schematically show a practical embodiment of aninternal combustion engine, a one-cylinder engine in this embodiment,which comprises such a crank-connecting rod mechanism. A number of theparts which are shown in FIGS. 1 and 2 are used as twin parts, one ofeach being used on either side of second crank 4 in this embodiment. Thedrawings demonstrate the great advantages of the use of second crank 4as second crank pin 6, because the crankshaft can continue now and neednot be divided, while this furthermore leads to a very compactconstruction. Only bearing 11 of connecting rod 12 has a relativelylarge diameter.

FIGS. 4a-i how the operation of the crank-connecting rod mechanism,wherein it can be clearly recognized that the gear comprising thecounterweight 10 rotates in opposite direction at the same rotationalspeed as first crank 2, and that it makes an exactly vertical movement,due to the use of the same radial distances R₁ and R₂, with a strokewhich equals 2*(R₁+R₂). It has already been indicated in theintroduction what advantages this may provide, in particular in the caseof a two-stroke engine.

It is noted that the vertical movement of connecting rod 12 can also beeffected with rotary means other than gear 8 and ring gear 9. Thus itwould for example be possible to fit connecting rod 12 or bearing 11with a guide which prevents connecting rod 12 from moving in lateral orhorizontal direction. In this manner the second crank 4 is forced into avertical path by the connecting rod 12 itself and rotated a fixedrotation with respect to the first crank pin 3. Also other rotary meansare conceivable, of course.

FIGS. 5-7 show a more practical version of the embodiment of thecrank-connecting rod mechanism as schematically shown in the precedingfigures, wherein also part of the surrounding combustion engine isshown. The crank-connecting rod mechanism is mirror-symmetrical oneither side of connecting rod 12. In the figures, first shaft 1 can bedistinguished, which shaft is mounted in a bearing 15 (FIGS. 6, 7), forexample a ball bearing. Eccentrically positioned in first crank 2 withrespect to first shaft 1 is a bearing recess which houses a bearing 17,which functions to receive the first crank pin portions 6′ and 6″ of thetwo crankshaft halves in the form of mutually fitting parts so as toassemble the two crankshaft halves into a crankshaft.

The crankshaft is fitted with a first counterweight 18 of first crankpin 2 and a second counterweight 19 of second crank 4. As can be seen inthe various figures, gear 8, which makes up the rotary means for firstcrank pin 3 and which meshes with ring gear 9, is disposed externally ofthe first counterweight 18, seen in axial direction. The bearing for thefirst crank pin 3 is positioned quite closely to second crank 4, as aresult of which the flexural strain on said first crank pin 3 willremain low. The fact is that first crank pin 3 is supported with asecond bearing 20 on the side of gear 8 remote from bearing 17 (seeFIGS. 6 and 7). The crankshaft locally exhibits great flexural strength,due to its large diameter, while crankshaft bearing 15 is disposed asclosely to the connecting rod 12 as possible.

The figures furthermore show that ring gear 9 is provided with elongatedmounting holes 21, which extend concentrically about the central axis ofthe internal teeth of ring gear 9, and which may be utilized forrotatably mounting ring gear 9. As can be seen in FIG. 7, a crankcasecover 22 of the combustion engine is provided with a closable adjustinghole 23, by means of which fastening screws (not shown) for the ringgear 9 can be tightened and loosened for the purpose of adjusting andfixing ring gear 9. Thus it is possible to effect a readjustment of ringgear 9 so as to obtain the truest possible movement of thecrank-connecting rod mechanism, that is, the most rectilinear possiblemovement of connecting rod 12 of piston 13.

FIG. 7 further shows the mounting of bearing 15 of crankshaft 1 incrankcase cover 22. FIG. 7 furthermore shows the construction of thecombustion engine as regards the piston 13 and the parts that co-operatetherewith.

Piston 13 moves up and down in a cylinder 24 which is provided withoutlet ports (not shown) and scavenge ports 25. FIG. 7 further shows acombined inlet and guide housing 26. Said housing 26 is provided with aninternal guide 26′ for guiding connecting rod 12. Said guide 26′ alsoseals off the space in cylinder 24 under piston 13, so that a scavengingpressure can be built up in said space. The shape of housing 25 isthereby such that the piston skirt closely surrounds said housing in thebottom dead center of piston 13, as a result of which the false volumein the scavenging space is minimal, thus enabling an optimum scavengingeffect.

Also the position of inlet membranes 27, which are mounted on theoutside of inlet and guide housing 26, contributes towards minimizingthe false volume. The supply of air, and possibly of fuel, takes placefrom an inlet channel 28 which connects to a channel 29 in housing 26,which channels are in communication with the inlets to be opened andclosed by membranes 27.

FIGS. 8 and 9 show another embodiment of the crank-connecting rodmechanism according to the invention, wherein essentially the same partsare used as in the first embodiment according to FIGS. 1-4, but whereinthe relative proportions and the positions of parts are different. Inthis embodiment, for example, the diameter R₃ of gear 8 is twice aslarge as the radial distance R₁ of first crank pin 3, as a result ofwhich the rotational speed of second crank 4 is half the rotationalspeed of first crank 2, while the direction of rotation is opposedthereto. This results in an entirely different movement of second crankpin 6 in comparison with that of the first embodiment. In the firstplace, the horizontal movement of the first crank pin 3 is no longercompensated, so that connecting rod 12 can no longer reciprocatevertically, thus making it necessary to use a conventional connectingrod 12. Furthermore it can be seen, for example in FIG. 8a, that whenfirst crank pin 3 occupies its uppermost position, second crank pin 6does not occupy its uppermost position, but its middle position, so thatsaid crank pins are angularly offset 90° with respect to each other insaid uppermost position. The second radial distance R₂ of second crankpin 6 may be different from first radial distance R₁ in this case (dueto the fact that it is no longer necessary to provide horizontalcompensation) and it is possible to determine the relative proportion oftwo successive strokes of piston 13. Because second crank 4 moves athalf speed, second crank 4 will only make a semi-revolution while crank2 makes a complete revolution, so that a full cycle of thecrank-connecting rod mechanism will only be completed after tworevolutions of first crank 2. In the illustrated embodiment, the firstand the second stroke of piston 13 ((long) expansion and exhaust stroke)equal 2×R₁+R₂ (the travel of piston 13 between the positions shown inFIGS. 8a and 8 c, or 8 c and 8 e), while the third and the fourth strokeequal 2×R₁−R₂ (the travel of piston 13 between the position according toFIGS. 8e and 8 g, or 8 g and 8 i).

As already described in the foregoing, such an embodiment of thecrank-connecting rod mechanism according to the invention makes itpossible to construct a four-stroke engine in which the compressionstroke and the expansion stroke are different from each other, which isdone in order to utilize the expansion forces better.

FIG. 9 shows the same construction as FIG. 8, but in this case ring gear9 is turned clockwise through an angle (in this case 11°) in comparisonwith the symmetric position as shown in FIG. 8, which angulardisplacement can be recognized from the position of a point 14 on ringgear 9. In this case the second crank pin 6 does not occupy its middleposition when first crank pin 3 occupies its the uppermost position(FIG. 9a), and in the position which is shown in FIG. 9a, wherein theextreme compression position is illustrated, the position of piston 13is lower than the position according to FIG. 8a, as a result of whichthe end compression will be lower. Rotation of ring gear 9 thus makes itpossible to opt for a lower end compression in full load conditions orwhen a charging pressure is used (or, in the case of rotation in theother direction, for a higher end compression in part load conditions).The position of the top dead center at the end of the exhaust stroke(FIG. 9c) has been raised in comparison with the position as shown inFIG. 8e, by the same value as the value by which the position of theupper dead center at the end of the compression stroke has been lowered.Also the position of the bottom dead center at the end of the expansionstroke and the inlet stroke will be different, but as a result of thenearly vertical position of the second crank pin 6 in the bottom deadcenter, angular displacement of the second crank pin 6 about saidposition will influence the position of the bottom dead center lessstrongly.

It will be apparent that rotation of ring gear 9 during operation of thecombustion engine will be capable of effecting an adjustment of theengine characteristic, so that electronic control of said rotation ofring gear 9 can lead to an optimum operation of the combustion engine independence on the particular load condition at that moment.

FIGS. 10 and 11 show a practical embodiment of the crank-connecting rodmechanism of FIGS. 8 and 9. In this embodiment, a very compactconstruction has been obtained in that ring gear 9 is disposed centrallyand the first and the second crank pin 3 and 6 are positioned withinsaid ring gear 9, seen in axial direction. The big end bearing ofconnecting rod 12 surrounds an eccentric portion 6 of second crank 4,which thus forms second crank pin 6. Second crank 4 is provided oneither side of second crank pin 6, and consequently on either side ofconnecting rod 12, with gears 8 which mesh with each of the internalteeth 9′ of ring gear 9. Ring gear 9 is provided between its teeth witha passage 30 for connecting rod 12. Second counterweight 10 isintegrated in second crank 4. Facing grooves 31 formed round the centralaxis of the first crank pin 3 provide accommodation for an outer portionof second crank 4, thus enabling further dimensional minimization.

FIG. 12 shows another practical embodiment of the crank-connecting rodmechanism which is intended for use in a multicylinder engine whosecylinders are arranged in the form of a V or in flat oppositerelationship. In this embodiment, gear 8 is disposed between the twosecond cranks 4 of the two connecting rods 12, and ring gear 9 islikewise disposed between the two connecting rods 12. In this manner avery compact construction is realized.

FIGS. 13-15 show another variant in this case for a four-cylinder,four-stroke in-line engine. As is shown in the figures, the rotary means7 for the two second cranks 4 are mounted between two adjacent cranks 4,which are angularly offset 180° relative to each other. Each secondcrank 4, has a gear 8 mounted directly adjacently thereto, so that nospace is lost between them. Ring gear 9 surrounds gear 8. Presentbetween the adjacent ring gears 9 is an intermediate ring 31, which isrotatably accommodated in the crankcase in this embodiment. Theintermediate ring is fixed to the two adjacent ring gears 9 by means ofbolts (not shown). Present inside the intermediate ring 31 is a bearing32, which functions to rotatably support the respective portion 33 ofthe crankshaft. Said crankshaft portion 33 furthermore carries acounterweight 34, which closely surrounds gear 8 and which does notoccupy any additional axial space, therefore.

For the purpose of adjusting rotary means 7 while the combustion engineis running, intermediate ring 31 is provided with a control pin 35,which slidably engages in a bush 36, which bush is rotatablyaccommodated in a control valve 37 which is used for the two controlpins 35 jointly. Control valve 37 may for example be fitted with aspindle nut 38, which cooperates with a spindle which can be rotatablydriven, for example by means of a stepping motor 50, which makes itpossible to move control valve 37 precisely so as to rotate intermediatering 31 and thus the ring gears 9 for adjusting the compression endpoint and the expansion end point of the stroke of pistons 13.

The illustrated construction of the crankshaft and rotary means 7enables the use of a standard cylinder block, because it is possible touse the same center-to-center distance between pistons of a conventionalfour-cylinder engine, and only the crankcase needs to be adapted to thenew construction of the crankshaft.

From the foregoing it will be apparent that the invention provides acrank-connecting rod mechanism which provides surprising newpossibilities for optimization of the operation of a piston engine orother machine without any complicated measures being required.

The invention is not restricted to the above-described embodiments asshown in the drawing, which can be varied in several ways withoutdeparting from the scope of the invention. Thus it is also possible touse the invention with crank mechanisms of other machines, such ascompressors or other machines wherein rectilinear motion is convertedinto rotary motion, or conversely. In the case of piston engines, theinvention also relates to multi-cylinder engines in various arrangementsthereof.

What is claimed is:
 1. A crank-connecting rod mechanism for an internalcombustion engine or the like having a compression stroke and anexpansion stroke, comprising an assembly of: a shaft rotating about itsaxis; a first crank fixed to said shaft; a crank pin fixed to said firstcrank, which extends parallel to but at a first radial distance fromsaid shaft; a second crank rotatably mounted on the first crank pin,which is fixed to a second crank pin having an axis at a second radialdistance from the axis of the first crank pin, wherein the first andsecond cranks are in such relative positions that, at an uppermost pointof the compression stroke, the first crank is positioned at 0° and thesecond crank is positioned at substantially 90° such that the first andthe second cranks are both positioned at substantially 180° at the endof the expansion stroke; a connecting rod which is rotatably mounted onthe second crank pin; and rotary means for causing the second crank torotate relative to the first crank upon rotation of the shaft, whereinthe rotary means is so arranged that the second crank rotates at halfthe speed, albeit in an opposite direction, of the first crank.
 2. Thecrank-connecting rod mechanism according to claim 1, wherein the firstradial distance is equal to or different from the second radialdistance.
 3. The crank-connecting rod mechanism according to claim 1,wherein said rotary means comprises at least two parts, a first partthat is rotatably mounted on the second shaft and fixedly connected tothe second crank, and a second part that is in engagement with saidfirst part.
 4. The crank-connecting rod mechanism according to claim 3,wherein said first part is a gear and said second part is a internalring gear that meshes with the first gear, wherein said ring gear iscentrally disposed, extending on a side of the connecting rod.
 5. Thecrank-connecting rod mechanism according to claim 4 for use in at leasta four-cylinder engine, wherein the the crank-connecting rod mechanismincludes the assembly for each cylinder wherein each first gear isdisposed directly adjacent to the associated second crank and connectingrod, and wherein each ring gear is disposed on a side of eachcorresponding connecting rod such that the ring gears are disposedbetween staggered second cranks of the shaft, and wherein a crankshaftbearing is disposed between the two ring gears of the staggered secondcranks.
 6. The crank-connecting rod mechanism according to claim 5,wherein two adjacent ring gears are mounted on an intermediate ring thatsupports said crankshaft bearing.
 7. The crank-connecting rod mechanismaccording to claim 4, wherein said ring gear is maintained in asubstantially stationary position during the operation of thecrank-connecting rod mechanism.
 8. The crank-connecting rod mechanismaccording to claim 4, wherein said ring gear is adjustable through anangle.
 9. The crank-connecting rod mechanism according to claim 8, andfurther comprising a motor coupled to rotate the ring gear.
 10. Thecrank-connecting rod mechanism according to claim 5, wherein at leastone of the first crank and the second crank of each assembly is providedwith a counterweight, and wherein said gear is mounted externally ofsaid counter-weight, and wherein a bearing is mounted internally of saidgear for supporting the first crank pin.
 11. The crank-connecting rodmechanism according claim 1, wherein the second crank itself is in theform of a second crank pin, and wherein a central axis of the secondcrank forms the axis of the second crank pin, and wherein the connectingrod is bearing-mounted about the second crank.
 12. The crank-connectingrod mechanism according to claim 4, wherein the gear is mounted on adisc in the form of a counterweight.
 13. A piston engine fitted with acrank-connecting rod mechanism according to claim
 1. 14. A piston enginefitted with the crank-connecting rod mechanism according to claim 8, andfurther comprising a crankcase surrounding the crank-connecting rodmechanism, the crankcase including an adjusting hole for adjusting thering gear from outside the crankcase.
 15. A cylinder and piston blockassembly comprising: a cylinder block having at least one cylinder; apiston movable in each cylinder wherein displacment of the pistonincludes a compression stroke and an expansion stroke; and for eachpiston, an assembly comprising: a shaft rotating about its axis; a firstcrank fixed to said shaft; a crank pin fixed to said first crank, whichextends parallel to but at a first radial distance from said shaft; asecond crank rotatably mounted on the first crank pin, which is fixed toa second crank pin having an axis at a second radial distance from theaxis of the first crank pin, wherein the first and second cranks are insuch relative positions that, at an uppermost point of the compressionstroke, the first crank is positioned at 0° and the second crank ispositioned at substantially 90° such that the first and the secondcranks are both positioned. at substantially 180° at the end of theexpansion stroke; a connecting rod connected to the pistion androtatably mounted on the second crank pin; and a rotary means forcausing the second crank to rotate relative to the first crank uponrotation of the shaft, wherein the rotary means is so arranged that thesecond crank rotates at half the speed, albeit in an opposite direction,of the first crank.
 16. The block assembly according to claim 15,wherein the first radial distance is equal to or different from thesecond radial distance.
 17. The block assembly according to claim 15,wherein said rotary means comprises at least two parts, a first partthat is rotatably mounted on the second shaft and fixedly connected tothe second crank, and a second part that is in engagement with saidfirst part.
 18. The block assembly according to claim 17, wherein saidfirst part is a gear and said second part is a internal ring gear thatmeshes with the first gear, wherein said ring gear is centrallydisposed, extending on a side of the connecting rod.
 19. The blockassembly according to claim 17, wherein the block assembly comprises aplurality of cylinders and pistons, and wherein said first part of eachrotary means is a gear and said second part of each rotary means is aninternal ring gear that meshes with the first gear, wherein said ringgear is disposed on a side of each corresponding connecting rod suchthat the ring gears are disposed between staggered second cranks of theshaft.
 20. The block assembly according to claim 19, wherein the blockassembly comprises at least four cylinders, wherein each first gear isdisposed directly adjacent to the associated second crank and connectingrod, and further comprising a crankshaft bearing disposed between thetwo ring gears of the staggered second cranks.
 21. The block assemblyaccording to claim 20, wherein two adjacent ring gears are mounted on anintermediate ring, and wherein the intermediate ring supports saidcrankshaft bearing.
 22. The block assembly of claim 21 wherein theintermediate bearing rotates the ring gears during operation.